Aluminum anodes and method of manufacture thereof

ABSTRACT

A process of making an aluminum alloy anodic material having improved electrochemical properties for use in an electrochemical cell and battery, the alloy consisting essentially of 95-99.5% w/w Al and 0.5-5.0 cumulative w/w additive metal selected from Group II-Group V metals of the Periodic Table, the process comprising heating 95-99.5% w/w Al and 0.5-5.0 cumulative % w/w additive metal in admixture to a temperature to form a homogeneous matrix of melted alloy; cooling the melted alloy at a liquidus/solidius cooling rate to produce a solid, non-equilibrium alloy of a non-homogenous multiphase matrix comprising discrete, relatively large crystals of pure aluminum and relatively smaller crystals of the additive metal included at the interface with the aluminum crystals; rolling the solid alloy to reduce its thickness to a factor of 0.2 to 0.01 to produce a rolled sheet of the alloy having a microstructure comprising an aluminum matrix having elongate inclusions of the additive metal and small, satellite ovoidal inclusions of the additive metal dispersed in the matrix.

FIELD OF THE INVENTION

[0001] This invention relates to improved aluminum alloy anodes, tobatteries and fuel cells comprising said anodes and to methods ofmanufacture of said anodes.

BACKGROUND OF THE INVENTION

[0002] Aluminum anode/metal-air cathode batteries and fuel cells requirea combination of competing electrochemical properties to be of practicaland, particularly, commercial value.

[0003] On one hand, the anode must be sufficiently highly active toprovide high voltage and current, while on the other hand, the anodeshould not be active, i.e. corrode, when there is no power loadrequirement. The anode should also uniformly react at its surfacewithout pitting or selective dissolution. Metals such as aluminum, zincand magnesium in pure and technical grade form, i.e. greater than 99.5%purity do not provide a favourable balance of aforesaid electrochemicalproperties and, thus, are alloyed in admixture with suitable, but smallamounts of additive metals to enhance electrochemical performance.

[0004] Metal alloying additives which improve the performance of thepure metals are known. For example, U.S. Pat. No. 4,098,606 disclosesthat the addition of indium, gallium or thallium of 0.01-0.5% by weight,are beneficial for producing an active aluminum alloy.

[0005] U.S. Pat. No. 4,792,430 discloses that addition of 0.03-0.2% tinto aluminum is beneficial in which the benefit can be further enhancedby the addition of 0.03-0.07% gallium and/or 0.002 to 0.006% silicon.These beneficial alloys are produced by preparing a homogeneous mixtureof the elements above their melting points and then subsequently coolingthe mixture to produce a solid phase having the desired elements attheir appropriate concentration.

[0006] The process of alloying aluminum, magnesium and zinc metals formodification of physical properties, such as strength or magneticproperties is well-known. For example, U.S. Pat. No. 4,294,625 disclosesthat aluminum may be given enhanced properties of strength, fatigueresistance and fracture toughness by the weight addition of 3.8-4.4%copper, 1.2-1.8% magnesium, 0.6-0.9% manganese, and less than 0.12%silicon, 0.15% iron, 0.25% zinc, 0.15% titanium, 0.1% chromium and 0.05%other elements.

[0007] Other processes disclose the improvement of physical propertiesby providing specific cooling rates to the molten alloy. U.S. Pat. No.4,126,486 discloses that an aluminum alloy containing 4-15% silicon maybe strengthened by solidifying the molten alloy at a specific rateduring casting and then further treating the alloy to a rolling processand finally an annealing process at 250-400° C.

[0008] The process of producing an alloy in which the alloying componentis supersaturated has also been described. For example, U.S. Pat. No.5,585,067 describes a process for mixing the molten alloy during thecooling stage such that a 2-phase dispersion of small-sized,well-dispersed inclusions is created. The supersaturated components werebismuth, cadmium, indium or lead. Other patents have described thebenefits of keeping the additives in the aluminum phase by rapid coolingof the aluminum melt. United States RE 34,442 describes the productionof an aluminum ingot having magnesium and silicon as strengtheningagents, which are prevented from forming a separate phase by quickcooling of the melt. By keeping the additives in the aluminum matrix ina dissolved state, the extrudability of the alloy is improved. Otherpatents, such as U.S. Pat. No. 4,805,686 disclose that the rapidquenching is beneficial for producing a microeutectic microstructurewhich has high strength at elevated temperatures. The achievement ofuniform, fine grain structure disclosed in U.S. Pat. No. 4,490,188 isimportant in the 2000 and 7000 class aluminum alloys because it allowscold rolling to be performed on the alloy without cracking of thealuminum sheet. The fine grained microstructure has also been achievedin U.S. Pat. No. 4,415,374 by heating an alloy which has been solidifiedwith a second solid phase, to the melting point of the matrix, but belowthat of the second phase. Subsequent cooling of the melt yields afine-grained microstructure. U.S. Pat. No. 5,009,844 discloses theprocessing of aluminum alloy with a hypoeutectic composition by heatingat a finite (<20° C./min) rate such that partial dissolution of thesecond phase occurs. A more uniform and spherical second phase residueis left after treatment. A process of converting an alloy with adendritic second phase into a uniformly dispersed second phase in a castproduct is described in U.S. Pat. No. 5,911,843. The process usesthermal treatment which does not melt the alloy but allows the dendriticsecond phase to become dispersed.

[0009] The processing of aluminum alloys by means of rolling to producea sheet form is also known. Alloy composition and the hot and coldrolling conditions must be carefully controlled if a satisfactory rolledsheet product is to be produced. U.S. Pat. No. 5,080,728 discloses theconditions required for an aluminum alloy containing 0.7-1.15% iron plus0.5-2.0% manganese plus <0.6% silicon with the remainder being aluminumand inherent impurities (<0.03%). It is common to try to keep the secondphase or intermetallics well dispersed and with small grain size i.e.<11 um, as seen in U.S. Pat. No. 5,116,428.

[0010] The aforesaid prior art has used composition and processingconditions to improve physical properties of the final alloy. However,none has disclosed that the electrochemical activity of an anode mightalso be improved by modifying the physical structure of the alloy. Ingeneral, it is believed that chemical activity is due to the chemicalspecies present and not to their physical distinction.

[0011] There is a need, therefore, for an anodic material havingimproved electrochemical properties for use, particularly in batteriesor fuel cells.

SUMMARY OF THE INVENTION

[0012] It is an object of the present invention to provide a process forproducing an anodic material having improved electrochemical properties,such as, relatively higher current density, more efficient volt/amperecharacteristics, and superior discharge properties.

[0013] It is a further object to provide an anodic material havingaforesaid improved electrochemical properties.

[0014] It is a further object to provide said anodic material havingaforesaid improved electrochemical properties made from so-calledtechnical grade materials, particularly containing small amounts of Fe.

[0015] It is a further object to provide a battery having an anodeformed of a material having aforesaid improved electrochemicalproperties.

[0016] The present invention provides that by a new physical process ofhomogeneous alloy melt formation with quenching at a rapid rate,followed by hot and/or cold rolling, improved electrochemical propertiesare achieved from alloys that would otherwise be considered to have lowor no electrochemical property value. The improvement in electrochemicalbehavior, without being bound by theory is postulated to be the resultof a two phase structure of inclusions and matrix developed by the newphysical processing, which phase structure can be observed by opticaland electron microscopy. Unexpectedly, the preferred physical structureseen in the present invention is not the uniform, small inclusion sizefavoured for producing good physical strength characteristics noted inthe prior art but that having two types of inclusions, viz, largerdendritic inclusions comprising the majority of the metal additive and afinely dispersed inclusion making up the remainder of the metaladditive. A small amount of the metal additive ends up dissolved in thealuminum matrix. Characterization of the structures of conventionalprior art alloys and processed alloy of the same composition accordingto the invention shows that there is substantial physical difference inthe materials. The preferred performance is obtained when the alloy,according to the invention, has been processed to provide >80% of themetal additive inclusions in elongated dendritic form and the remainderof the inclusions as dispersed relatively very tiny particles.

[0017] Accordingly, in one aspect, the invention provides a process ofmaking an aluminum alloy anodic material having improved electrochemicalproperties for use in an electrochemical cell, said alloy consistingessentially of 95-99.5% w/w Al and 0.5-5.0 cumulative w/w additive metalselected from Group II-Group V metals of the Periodic Table, saidprocess compromising heating 95-99.5% w/w Al and 0.5-5.0 cumulative %w/w addictive metal in admixture to a temperature to form a homogeneousmatrix of melted alloy; cooling said melted alloy at a liquidus/soliduscooling rate to produce a solid, non-equilibrium alloy of anon-homogenous multiphase matrix comprising discrete relatively largecrystals of pure aluminum and relatively smaller crystals of saidadditive metal included at the interface with said aluminum crystals;rolling said solid alloy to reduce its thickness to a factor of 0.2 to0.01 to produce a rolled sheet of said alloy having a microstructurecomprising an aluminum matrix having elongate inclusions of saidadditive metal and small, satellite ovoidal inclusions of said additivemetal dispersed in said matrix.

[0018] Preferably, the additive metal is selected from Ga, In, Tl, Cd,Sn, Pb, Mn, Fe, and Mg; and more preferably, Mn, In, Sn and Fe.

[0019] In the alloy cooling step according to the invention, anon-equilibrium multi-phase structure having large pure Al crystals ofall shapes as one phase up to 5 cm long is produced and wherein theadditive metal(s) are occluded at the Al periphery as one or more phasesif one of more additive metals are present. The aluminum crystals orgrains in the pre-rolled alloy, thus, preferably, have an average lengthselected from about 1-5 cm.

[0020] It is known that when solidification of a melted homogeneousaluminum alloy is carried out slowly, equilibrium conditions can bemaintained during solidification. However, equilibrium conditions arenot attained in commercial casting techniques, and so-called“non-equilibrium” or meta-stable alloys are produced. The term“non-equilibrium” is understood in the art and reference is made to thetreatise: Aluminum: Technology, Applications and Environment—“A Profileof a Modern Metal”, Aluminum from Within—the Sixth Edition by DietrichG. Althenpohl, The Aluminum Association, Inc. 900 19th Street, Suite300, Washington, D.C. and The Minerals, Metals and Materials Society(TMS), 420 Commonwealth Drive, Warrendale, Pa.

[0021] In commercial casting processes, solidification rates and coolingof the solidified structure are closely tied together by the rapid heatremoval per unit of time. Especially in direct chill or strip castingtechniques, solidification and cooling after solidification is so rapidthat, in addition to the grain segregation, a considerablesupersaturation of the alloying elements occurs.

[0022] The term “liquidus/solidus cooling rate” in this specificationmeans the cooling rate of about 10kg of a 3cm thick alloy matrix in arectangular mould when cooled over the liquidus/solidus stage, i.e. fromthe temperature at which solidification of the melted alloy commences tothe temperature at which it has completely solidified. Thissolidification temperature range is, for example, typically, about20-30° C. for alloy compositions of use in the practice of theinvention, which commence to solidify at about 660° C. and areessentially solid at about 640° C.

[0023] A preferred cooling rate is selected from about 1° to 10° C. perminute, and more preferably selected from 2° to 5° C. per minute.

[0024] The alloy cooling step in the practice of the present inventionmay be suitably and readily achieved, preferably, for example by aircooling. The melted admixture is cooled at such a rate as to produce anon-equilibrium, solid alloy, multi-phase matrix, as hereinabovedefined. If the melt is cooled too quickly, a homogeneous multi-metallicphase having no or little discrete crystals is obtained. If the coolingrate is too slow, multi-phases of the different metals, each asrelatively large inclusions, non-uniformly distributed throughout thethickness of the mass is undesirably obtained.

[0025] The melted alloy may be readily melted and transferred to atypical mould for cooling at the aforesaid desired rate. An essentiallyrectangularly shaped, mould of internal dimensions selected, forexample, from 3-5 cm, wide, 5-20 cm long and 10-50 cm high toaccommodate 1-10 Kg alloy may be used.

[0026] The microstructures may be viewed by optical and electronmicroscopy.

[0027] The rolling step of use in the practice of the invention maycomprise either hot rolling or cold rolling techniques or, preferably,conventional hot rolling at a temperature selected from 200-560° C.,followed by cold rolling. Reductions by hot rolling to 10-20% of theoriginal thickness, followed by further reductions to 2-10% of theoriginal thickness by cold rolling is most preferred. The resultingthickness of the rolled plate, sheet, film, foil and the like of theorder of 0.2-2 mm, preferably, about 0.5 mm is of particular value as ananodic material in the practice of one aspect of the invention, inbatteries, and have been found to provide enhanced current densityactivity.

[0028] Without being bound by theory, we believe that the cold rollingstep, in particular, causes the aluminum crystals to merge under theshearing action to form a bulk matrix, and the relatively large additivemetal occlusions to elongate as occlusions within the aluminum matrix,which occlusions are surrounded by a plurality of much smaller,fragmented satellite additive metal occlusions dispersed in the matrix.The rolling steps are beneficially enhanced by use of lubricating oils.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order that the invention may be better understood, preferredembodiments will now be described, by way of example only, withreference to the accompanying drawings wherein

[0030] FIGS. 1A-1D represent electron microscopic images of analuminum/indium cast alloy according to the invention; FIGS. 2A-2Drepresent electron microscopic images in cross-section perpendicular tothe direction of rolling of the alloy of Example 1 after rolling asdescribed therein;

[0031]FIG. 3 represents a sketch of a test cell used to determine anodepotentials and corrosion rates of anode alloys according to theinvention;

[0032]FIG. 4 represents graphs of the polarization characteristics Pa(anode) as a function of current density of test anodes of 99.4% w/w (Al99.95% pure)+0.6% In, manufactured by different methods;

[0033]FIG. 5 represents graphs of the discharge characteristics Pa(anode) of the anode materials manufactured as described with referenceto FIG. 4;

[0034]FIG. 6 represents curves showing the dependency of the corrosioncurrent density I(corr.) on the relative amount of additive in anodematerials manufactured as described with reference to FIG. 4;

[0035]FIG. 7 shows comparative graphs of the polarizationcharacteristics Pa(anode) in volts as a function of current density ofseveral test anodes with various additive metals manufactured bydifferent methods;

[0036]FIG. 8 represents graphs of the discharge characteristicsPa(anode) volts of various anode alloy materials as described withreference to FIG. 7; and

[0037]FIG. 9 represents graphs showing comparative corrosion currentdensities against anode current densities for the alloys described withreference to FIGS. 7 and 8, manufactured according to the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS EXAMPLE 1

[0038] Al (9.5Kg. 99.95% purity) and In (0.5Kg.) were melted inadmixture to just above its melting point at about 660° C. and forcedair-cooled in a carbon-lined, rectangularly-shaped chamber having awidth of 3 cm, over a period of 30 minutes, and a crystallizationliquidus/solidus temperature range of about 20° C. to achieve theaforesaid non-equilibrium, homogeneous, crystal-forming conditionsdistinct from non-heterogeneous amorphous solidification.

[0039] The resultant alloy plate was hot-rolled at 500° C. to athickness of about 3 mm and cold rolled to a thickness of about 0.5 mm.

EXAMPLE 2

[0040] Example 1 was repeated wherein a 10cm thick amount of the meltedalloy of Example 1 was air-cooled over a period of 10 hours.

EXAMPLE 3

[0041] Example 1 process conditions were repeated with a 99.7%aluminum/0.3% indium alloy.

[0042] With reference to FIG. 1, this shows electron microscopicstructures of the aluminum/indium alloy cast according to Example 1prior to hot/cold rolling. FIGS. 1A and 1B, enlarged ×200 and ×400,respectively, show large aluminum crystals of 1.5 cm length havingindium colonies on the periphery of the aluminum grains. FIG. 1C at anenlargement of ×4000 shows indium colonies as spherical bodies ofapproximately 1.6 micron diameter or elongated occlusions ofapproximately 10 microns in length. FIG. 1D shows the internal structureof the indium colony at a magnification of ×10,000.

[0043]FIG. 2 shows the rolled alloy wherein FIGS. 2A and 2C represent astrip, foil and the like of thickness 1 mm at a magnification of ×2600and ×6000, respectively, while FIGS. 2B and 2D are 3 mm thick and at amagnification of ×2000 and ×6000, respectively. Satellite indiuminclusions of not larger than 0.1-0.2 micron diameter can be seen to beinterspersed among the larger elongate indium crystals.

[0044]FIG. 3 shows generally as 10 the test cell used to determine anodepotentials and rates of corrosion of the aluminum alloys under test.

[0045] Cell 10 has a cylindrical body 12 hermetically sealed betweenremovable end covers 14 against gaskets 16. Body 12 at an upper part hasa side tube 18 for release of hydrogen under test. Coaxial within body12 is a reference electrode 20 adjacent disc 22 of specimen anode undertest. Terminals 24, 26 are located at upper and lower covers 14,respectively for contact with electrode 20 and disc 22, respectively,for measuring Pr (reference) and Pa (anode), respectively. Cell 10contains aqueous potassium hydroxide (4 mol/L) electrolyte with 0.6% w/wpotassium stannate additive, 28. The temperature was controlled to thatspecified by the testing requirements.

[0046] With reference to FIG. 4, this shows the polarizationcharacteristics Pa (anode) as a function of current density of testanode alloys comprising 99.4% Al and 0.6% In, wherein the alloy is madeas follows.

[0047] Curve 1 is for the aforesaid alloy made according to the presentinvention, comprising the general steps of

[0048] a. casting and quick crystallization of the non-equilibratedalloy (fast quenching);

[0049] b. multi stage hot rolling; and subsequent

[0050] c. cold rolling as a finishing stage.

[0051] Curve 2 is as far as step a., only.

[0052] Curve 3 is cast and hot and cold rolled according to conventionalprior art manufacturing methods.

[0053] The polarization characteristics were measured at a temperatureof T=60° C. (333° C.). Curves 1, 2 and 3 show that the polarizationcharacteristics are not much different up to the current density ofJ=300-400 ma/cm². With further increase of the current density, thedifference between the polarization characteristics rapidly increases.

[0054] For example, for current density of J=500 ma/cm², the potentialPa (anode), curve 1 is about −1.50 V, for curve 2 it is −1.25 V, and forcurve 3 it is −1.3 V. For the current density of J=550 ma/cm² thedifference in the potentials on curves 1 and 3 is about 0.4 V; i.e. forthe invention anode curve 1, Pa (anode) is about -1.37 V, while for thetraditional technology, curve 3, it is about -0.93 V.

[0055] Accordingly, the efficiency of the anode electrode manufacturedaccording to the invention is superior for nominal and large currentloadings of the anode as compared to the regular anode alloys made usingthe method according to the prior art.

[0056]FIG. 5 shows the discharge characteristics against time for thethree anode materials manufactured as described with reference to FIG.4, in the same electrolyte composition and at the same temperature of60° C., and a discharge current density of 100 ma/cm², using the celldescribed in FIG. 3.

[0057] The results show that for the extended discharge cycles, theanode electrode according to the invention (curve 1) is superior overprior art alloy anode material (curve 3), in part related to the energycapacity, of approximately by 30-40%. The longer the discharge cycle,the better the electrochemical property of an anode material.

[0058]FIG. 6 shows corrosion current density I(corr.) curves formaterials made by each of the three methods of manufacture describedwith reference to FIG. 4, using the test cell described in FIG. 3 underthe same conditions of temperature in the same electrolyte.

[0059] The curves of FIG. 6 show that the anode alloy according to theinvention (curve 1) provides the most advantageous values of corrosioncurrent density from 10 to 20 ma/cm² within the range of from 0.05 to1.4% w/w of the additive In. The maximum value of the corrosion currentdensity of about 20 ma/cm² falls within the range of 0.5-0.8% w/w In.

[0060] It is worth noting that with the reduction of the concentrationof In in the alloy from 0.2 to 0.05% w/w, the corrosion current rapidlyincreases from 10 ma/cm2 to 20 ma/cm².

[0061] For prior art anode alloy (curve 3), the character dependency ofthe corrosion current density is about the same. However, the magnitudeof the corrosion density is about an order larger i.e. from 130 ma/cm²to 160 ma/cm². Gentle, but noticeable maximum corrosion current densityin the range 0.5 to 0.8% w/w In was observed.

[0062] For the non-rolled anode of alloy (curve 2) the characterdependency of the corrosion current density is significantly inferior.

[0063] Longer-term measurements were conducted to obtain themass-volumetric characteristics of the corrosion reaction of theaforesaid alloys having 0.6% In, according to the invention, in theaforesaid cell at an electrolyte temperature of 20° C. (293° K).

[0064] The results of multiple measurements showed that, on average, therate of hydrogen generation H₂ during the corrosion reaction is about0.66 mL/hr/cm², which corresponds to a corrosion current density of1.3-1.5 ma/cm².

[0065] With reference to FIG. 7, this shows a series of curves obtainedunder the same conditions and manner as described with reference to FIG.4, representing the polarization characteristics as a function ofcurrent density of test anode alloys comprising as follows:

[0066] In: 99.4%Al+0.6% In;

[0067] Sn: 99.85%Al+0.15%Sn;

[0068] Mn: 99.97%Al+0.03%/oMn;

[0069] Fe: 99.99%Al+0.01% Fe; and wherein in each trio of curves:

[0070] Lines 1 denote the respective aforesaid alloy made according tothe invention;

[0071] Line 2 denote the respective aforesaid alloy made according tothe pre-rolled invention process step only; and

[0072] Lines 3 denote the respective aforesaid alloy made according to aconventional prior art cast and hot and cold rolled manufacturingmethod.

[0073] The series of comparative curves show in each case for eachalloy, that the efficiency of the anode material made according to theinvention is superior to the same anode composition made according tothe prior art, and, indeed, when only the fast quenching step processused in the two-step process of the invention is used.

[0074]FIG. 8 shows discharge characteristics against time for the fourdifferent metal compositions, of anode materials manufactured asdescribed with reference to FIG. 7 in the same electrolyte composition,at the same temperature of 60° C., and a discharge current density of100 ma/cm² using the cell described in FIG. 3.

[0075] The results show that for the extended discharge cycles, theanode electrodes according to the invention (curves 1) are superior overcorresponding composition prior art alloy anode material (curves 3) andpre-rolled only materials (curves 2). The longer the discharge cycle,the better the electrochemical property of an anode material.

[0076] With reference to FIG. 9 this shows comparative graphs ofdifferent alloys made according to the method of manufacture accordingto the invention, as follows:

[0077] 1. 99.4%Al+0.6% In;

[0078] 2. 99.85%Al+0.15%Sn;

[0079] 3. 99.97%Al30 0.03%Mn;

[0080] 4. 99.99%Al+0.01% Fe (technical Al)

EXAMPLE 4

[0081] The anode material according to the invention as described underExample 1 was subjected to subsequent additional thermal treatment ofdifferent temperatures and time periods. The additional treatment stepsincluded, for example, tempering, annealing, and cooling as given inTable 1. Also given in Table 1 are the electrochemical values obtainedfrom the test cell described with reference to FIG. 3 operated at 60° C.Values of the anode potentials, corrosion rates and effective activationenergy—which is related to the corrosion current and temperature by theArrhenius Equation.

[0082] The relative errors of the measurements were as follows:

[0083] 2.8% for the anode potential Pa (anode)

[0084] 6.3% for the corrosion current density I(corr.)

[0085] 1 1.1% for the effective activation energy Ea. TABLE 1 EffictiveThermal Anode Corrosion activation treatment potential current density,energy, E_(a), mode V Pa (anode) I(corr.) a/m² kJ/mol Annealing, −1.884*242 46.6 1.5 hour cooing with −1.838⁺ furnace Annealing, −1.876* 26541.8 3 hours cooling with −1.854⁺ furnace Annealing, −1.871* 276 40.6 8hours cooing with −1.841⁺ furnace Tempering, −1.878* 276 43.3 10 min.cooling in −1.833⁺ water Tempering, −1.898* 231 47.2 25 min. cooling in−1.856⁺ water Tempering, −1.890* 272 40.4 40 min. cooling in −1.842⁺water

[0086] The results in Table 1 show several secondary thermal treatmentfeatures. The first is that even though the alloy composition is fixedfor all of the tests, the electrochemical behavior can be modified tosome minor degree by changing the cooling rates for the alloy. In theprior art, it has always been assumed that alloying by addition ofcertain specific elements to the base material is sufficient to provideadequate electrochemical properties. From the results in Table 1 it isclear that the electrochemical kinetic parameters, such as the effectiveactivation energy, can be modified by processing to provide additionalgood properties. From the processing results in Table 1, it can be seenthat a small activation energy 40.6 kJ/mole results in a relativelylarge corrosion current of 276 A/m2 while a high activation energy valueof 47.2 kJ/mole results in a smaller corrosion rate of 231 A/m2. Theunexpected aspect of the results is that processing affects such afundamental electrochemical characteristic as activation energy.Tempering for 25 minutes cooling in water produces an improvedelectrochemical property independent of the effect of alloy composition.Interestingly, this process condition also produces the best initial andfinal voltage. Thus, the physical processing method described, has theability to substantially improve the performance characteristics ofaluminum anode materials. By way of comparison, an alloy of similarcomposition produced conventionally, has an undesirable corrosioncurrent of 1700 A/m2 as shown in FIG. 6. The processing set forthclearly demonstrates a method to produce an anode material that hassuperior electrochemical properties; initially (high initial voltage seeTable 1); during discharge (high voltage during discharge at highcurrents, see FIG. 4); and at end of discharge by way of greatercapacity (smaller corrosion rates see FIG. 5).

[0087] In conclusion, the results show that anode alloys according tothe invention have about one order lower corrosion current densityrelative to the alloy of the same composition made according to theprior art, while having more efficient volt-ampere characteristics whenused at medium and particularly high anode current densities; and alsohas a relatively larger energy capacity to provide superior dischargecharacteristics.

[0088] Although this disclosure has described and illustrated certainpreferred embodiments of the invention, it is to be understood that theinvention is not restricted to those particular embodiments. Rather, theinvention includes all embodiments which are functional or mechanicalequivalence of the specific embodiments and features that have beendescribed and illustrated.

1. A process of making an aluminum alloy anodic material having improvedelectrochemical properties for use in an electrochemical cell, saidalloy consisting essentially of 95-99.5% w/w Al and 0.5-5.0 cumulativew/w additive metal selected from Group II-Group V metals of the PeriodicTable, said process compromising heating 95-99.5% w/w Al and 0.5-5.0cumulative % w/w additive metal in admixture to a temperature to form ahomogeneous matrix of melted alloy; cooling said melted alloy at aliquidus/solidus cooling rate to produce a solid, non-equilibrium alloyof a multiphase matrix comprising discrete, relatively large crystals ofpure aluminum and relatively smaller crystals of said additive metalincluded at the interface with said aluminum crystals; rolling saidsolid alloy to reduce its thickness to a factor of 0.2 to 0.01 toproduce a rolled sheet of said alloy having a microstructure comprisingan aluminum matrix having elongate inclusions of said additive metal andsmall, satellite ovoidal inclusions of said additive metal dispersed insaid matrix.
 2. A process as defined in claim 1 wherein said coolingrate of said melted alloy is selected from 1° to 10° C. per minute.
 3. Aprocess as defined in claim 2 wherein said cooling rated is selectedfrom 2-5° C. per minute.
 4. A process as defined in claim 1 whereinabout 80-90% w/w of said additive metal in said rolled alloy is in theform of said elongate inclusions and about 10-20% w/w is in the form ofsaid ovoidal inclusions.
 5. A process as defined in claim 1 wherein saidelongate inclusion has a length selected from 2-30 microns, a widthselected from 0.4-3 microns; and said ovoidal inclusion has a diameterselected from 0.1-0.3 microns.
 6. A process as defined in claim 1wherein said additive metal is selected from Ga, In, Tl, Cd, Sn, Pb, Mn,Fe, and Mg.
 7. A process as defined in claim 6 wherein said additivemetal is selected from Sn, In, Mn and Fe.
 8. A process as defined inclaim 6 wherein said alloy consists essentially of 99.4% w/w Al and 0.6%w/w In.
 9. A process as defined in claim 1 wherein said solid alloy ishot rolled to 10-20% of original thickness and subsequently cold rolledto 2-10% of original thickness.
 10. A process as defined in claim 1wherein said solid alloy is rolled to a thickness selected from 0.2-1mm.11. A process as defined in claim 1 wherein said aluminum crystals insaid pre-rolled solid alloy have an average length selected from up to 5cm and a width of 0.2-1 mm.
 12. An aluminum alloy having improvedelectrochemical properties for use as an anode in an electrochemicalcell consisting essentially of 95-99.5% w/w aluminum and 0.5-5.0cumulative % w/w additive metal selected from Group II-Group V metals ofthe Periodic Table, and having a microstructure comprising an aluminummatrix having elongate inclusions of said additive metal and smaller,satellite ovoidal inclusions of said additive metal dispersed in saidmatrix.
 13. An alloy as defined in claim 12 wherein about 80-90% w/w ofsaid additive metal is in the form of said elongate inclusions dispersedin said matrix.
 14. An alloy as defined in claim 12 wherein saidelongate inclusion has a length selected from 2-30 microns and a widthselected from 0.4-3 microns; and said ovoidal inclusions has a diameterselected from 0.1-0.3 microns.
 15. An alloy as defined in claim 12wherein said additive metal is selected from Ga, In, Tl, Cd, Sn, Pb, Mn,Fe, and Mg.
 16. An alloy as defined in claim 12 wherein said additivemetal is In at a concentration of about 0.5% w/w.
 17. An electrochemicalcell comprising an anode, a cathode, and an electrolyte, wherein saidanode is formed of an alloy as defined in claim
 12. 18. A batterycomprising an anode, a gas-diffusion cathode, and an alkali metalelectrolyte; wherein said anode is formed of an alloy as defined claim12 and is in the form of a tape, foil or sheet having a thicknessselected from 0.05 mm-2 cm.